Surgical operations typified by abdominal surgery, orthopedic surgery, neurosurgery and the like may have a problem of adhesion between organs, as a postoperative complication. It means that when normal tissues damaged with drying and oxidation in the surgery are sutured, organ tissues that should not join may be joined together to cause adhesion phenomenon in a process of self-cure of wound. Surgery operations are supposed to accompany the adhesion in a high rate, so that complications may cause pains or serious conditions such as intestinal obstruction (ileus) and infertility.
Once the adhesion occurs, medication treatment may not be effective. The adhesion may cause intestinal obstruction after some years from the surgery. The adhesion prevention is very important in a surgery operation because the adhesion can only be cured by the synechiotomy to peel adhered area by additional surgery operation.
For a postoperative treatment to prevent tissue adhesion and delayed cure, exposed organ tissues are conventionally covered with gauze immersed in saline to prevent drying and oxidation. However, soft and complicated organs may not be fully covered with gauze. Furthermore, a doctor may be disturbed with gauze in a surgery or forget to get rid of gauze from the body where much gauze is used.
For such reasons, organ tissues can be physically separated as using an adhesion prevention membrane made of material such as silicone, “Teflon” (registered trademark), polyurethane and oxycellulose, which perform adhesion prevention or delayed cure prevention. But these non-absorbable materials which tend to stay on a biotissue may delay the tissue restoration and cause infection or inflammation.
To solve such problems, Patent documents 1 and 2 disclose adhesion prevention materials made with gelatin or collagen which is expected to be bioabsorbable. However, it is difficult to remove antigenic telopeptide from the material made with gelatin or collagen. Also, they say such a material should not be used in the body in view of risk of infection such as prion contamination derived from animals. Further, it is thought that a cross-linker added to control the strength or degradability is often undesirable for in vivo use.
On the other hand, natural polymers having good affinity to skin may have poor strength. Therefore the natural polymers have to be reinforced, by cross-linking with cross-linker, by reinforcing with reinforcing material, by coating with gauze, or the like. The reinforcing material may not be practical in view of the complicated structure.
Patent document 3 discloses an adhesion prevention material made with polysaccharide such as trehalose having no risk of infection. However, such a material made with polysaccharides may not have sufficient strength and therefore may not be sutured because of poor strength in suturing. Even if it can be sutured successfully, it is difficult to maintain the sutured condition for a certain time.
Patent document 4 discloses an adhesion prevention material made with hyaluronic acid. But such a material has a poor adhesiveness to organs and tends to slide on the organ to cause adhesion. Therefore it may not have a sufficient ability. Further, it may be manufactured at a higher manufacturing cost because mass production is difficult. There are some ways to make the adhesion prevention membrane firmly adhere to organs or the like by using blood products or chemical substances. But such a membrane has to be handled carefully with a good hygiene and safety.
Although thus there are many reports about materials for adhesion prevention of tissues, there is no material that is sufficiently qualified as an adhesion prevention material. Accordingly, they require a material that can prevent an adhesion as maintaining the strength until the tissue is restored.